This invention relates to a device for obtaining a cooling curve of molten materials for the determination of the composition of the molten material by the thermal arrests occurring in the cooling curve.
U.S. Pat. No. RE 26,409 discloses an expendable phase change detector device for determining the composition of molten metal such as cast iron or steel by the measurement of thermal arrest by phase change detectors. As a sample of molten cast iron freezes, phase change or thermal arrest temperatures will correspond to the initial separation of austenite from the melt liquid (liquidus) and final solidification of the remaining liquid of eutectic composition (solidus). The device of No. RE 26,409 provided a liquidus arrest from which could be obtained the carbon equivalent value of hypoeutectic cast iron.
Subsequent to the invention of U.S. Patent No. RE 26,409, U.S. Pat. No. 3,546,921 issued to Bourke et al disclosed a method of producing an initial thermal arrest in the cooling of a molten sample of hypereutectic cast iron by introducing into the molten sample a stabilizing additive which retards primary graphite formation as the molten sample cools.
More recently there has been disclosed in a technical paper appearing in "Foundry Management and Technology" July 1974 entitled "Rapid Carbon Determination on the Shop Floor" by Alan Moore of the British Cast Iron Research Association (BCIRA) that the percent of carbon in hypoeutectic cast iron can be determined by measuring the temperature of the liquidus arrest and the temperature of the solidus arrest and taking the difference of these two temperatures. This technique requires the introduction of a stabilizing additive into the 30 molten metal which retards primary graphite formation as the molten sample cools.
In applying any of the foregoing techniques, it is important that the temperature of the molten sample be accurately measured at all times during its cooling and that nothing associated with the expendable phase change detector device introduce into the molten metal sample any contaminants and particularly no carbonaceous material.